One of the most problematic elements of Lancelot and Guinevere's love is identified in Book XIII of the work which examines the reasons Lancelot is not able to achieve the Sangreal. In a particularly low moment of defeat, after being ordered by a mysterious voice to leave a holy chapel because of his sinfulness, Lancelot confesses to the hermit the intemperate and lecherous nature of his love for Guinevere:
And he told there the good man of his lyff, and how he loved a queen unmeasurably and oute of mesure longe. And all my grete dedis of armys that I have done for the moste party was for the quenys sake, and for hir sake wolde do batalye were hit ryght other wronge. And never dud I batayle all only for Goddis sake, but for to wynne worship and to cause me to bettir to be beloved , and litill or nought I thanked never God of hit. (Malory, 559)
Lancelot's admission of the problematic nature of his love for Guinevere directly contradicts Malory's attempts in the prelude to Book XVIII to characterize the relationship as pure and idyllic. The relationship between the two lovers is at best dysfunctional, often prompting Lancelot to behave dishonorably for the sake of the queen. Lancelot's use of the phrase "oute of mesure" identifies the obsessive dynamics of their relationship.
Malory's praise of the pure summer love of Arthur's days, devoid of sinful lust, is further undermined by the hermit's counsel to Lancelot concerning his sin. Comparing Lancelot to a barren fig tree, the hermit explains why Lancelot failed miserably in the quest for the Sangreal:
Jesus went oute of the towne and founde in myddis the way a fygge tre which was ryght fayre and cursed the tre that bare no fruyte; that betokenyth the fyg tre unto Jeruselum that had levys and no fruyte. So thou, sir Lancelot, whan the Holy Grayle was bought before the, He founde in the no fruit, nother goof thought nother good wylle, and defoulded with lechory. "Sertes," seyde Lancelot, "all that ye have seyde ys trew..."
The above passage is important for a variety of reasons. First, it unequivocally identifies Lancelot's desire for his liege lord's wife as lecherous. Futhermore, it contains Lancelot's own acknowledgment of this fact. Indeed, "licorous lustis" is an element of their relationship. Though this passage does not specifically implicate Guinevere , it does reveal that Lancelot and Guinevere's relationship is not as pure as the prelude to Book XIX suggests.